"the solar wind – a continual stream of charged particles released from the Sun that fills the solar system."
https://www.nasa.gov/feature/goddard/2023/sun/nasa-missions-find-jetlets-could-power-the-solar-wind
"interstellar hydrogen density, about 120 hydrogen atoms in a quart-sized space."
https://www.nasa.gov/feature/goddard/2020/new-evidence-our-neighborhood-in-space-is-stuffed-with-hydrogen
"Hydrogen, the most common element in the Universe, makes up most of the sun and the solar wind. Helium is the second most abundant element, but it is much rarer in the solar wind than it is elsewhere in the Universe"
https://www.nasa.gov/centers/goddard/news/topstory/2007/solar_wind_speed.html
"At the orbit of the earth the average solar wind consists of a strongly ionized gas having a proton and electron density of about 3 - 10 particles per cubic centimeter, with an average flow velocity of approximately 400 km/s. Occasionally stream structures are detected in the steady solar wind, which have peak velocities which tend toward a mean of about 750 km/s near the earth. Occasionally impulsive events are detected with peak velocities in excess of 1000 km/s."
https://umbra.nascom.nasa.gov/spartan/the_solar_wind.html
"The solar wind consists of charged particles, mainly protons and electrons, emanating from the Sun in all directions at speeds of several hundred kilometers per second. The solar wind also contains, in much smaller amounts, positive ions stripped of many of their electrons by the extremely high temperatures of the Sun."
https://soho.nascom.nasa.gov/explore/lessons/compos9_12.html
"99.9 percent of the Universe is made up of plasma," says Dr. Dennis Gallagher, a plasma physicist at NASA's Marshall Space Flight Center. "Very little material in space is made of rock like the Earth."
https://science.nasa.gov/science-news/science-at-nasa/1999/ast07sep99_1/
"Drag is a force exerted on an object moving through a fluid, and it is oriented in the direction of relative fluid flow. Drag acts opposite to the direction of motion and tends to slow an object."
"This same force acts on spacecraft and objects flying in the space environment."
https://www.swpc.noaa.gov/impacts/satellite-drag